The invention relates to vanadyl ion compositions which promote plant growth, especially plant fruit growth, and methods of applying the vanadyl ion compositions. Specifically, the compositions include organic compounds or complexes of vanadium. The vanadium compound or complex provides a source of vanadyl ions which are effective for promoting plant growth. The compositions may be prepared in concentrate form or application form. Effective amounts of the compositions when applied to plants during their growth period, promote plant growth, especially plant fruit growth.
The need for improving the yield and efficiency of horticultural and agricultural crops is becoming more critical as the population of the earth increases and the amount of arable land decreases. Consequently, researchers seek ways to improve the yield of plants through the use of materials which may be used economically as fertilizers, micro-nutrients, and growth promoters for various plants.
Various compositions have been studied as micro-nutrients and plant growth promoters to increase crop productivity across a wide range of horticultural and agricultural crops. Compositions which include vanadium compounds have been studied in this context, and have shown both beneficial and detrimental effects on plants. Vanadium occurs in the tops of higher plants at levels usually between 0.2 and 4 ppm. For example, vanadium (in the form of a solution of ammonium vanadate at a vanadium concentration of 20 micrograms per liter of nutrient solution) has been shown to be an essential element for unicellular plants such as algae. Arnon et al. 172 NATURE 1039-40 (1953). Further, while vanadium has stimulated growth in maize plants at levels of 0.25 ppm in nutrient solutions, it had no effect on lettuce and tomato plants at levels of 0.05 ppm. Lauchli et al. 15B ENCYCLOPEDIA OF PLANT PHYSIOLOGY 723-26 (1983). A study of the effect of a foliar spray of a vanadyl sulfate solution on leaf growth of sugar beet plants indicated that it decreased leaf growth, but that it increased the amount of reducing sugar in the roots of the sugar beet. Singh et al. 44 PLANT PHYSIOLOGY 1321-27 (1969). The use of vanadium (in the form of vanadyl lactate at concentrations of 10.sup.-3 to 10.sup.-6 molar) as a fertilizer has produced an increase in foliage yield of some higher plants. Kerr et al. Monograph 11 BRITISH PLANT GROWTH REGULATOR GROUP 103-21 (1984).
These studies indicate that vanadium may have some effect on plants, including higher order plants which are of agricultural interest. Whether that effect is beneficial or detrimental appears to depend on the form of the vanadium, the type of plant, and the method and timing of the application. Thus, a need exists to develop an effective vanadium composition and method for applying it that will promote the growth of agriculturally useful plants.